Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for setting uplink transmission power in a wireless communication system, which support a plurality of component carriers.
Related Art
In recent years, the commercialization of long term evolution (LTE) systems, that is, next-generation wireless communication systems, is being supported in earnest. The LTE system is spread more rapidly as a need to guarantee the activity of UE users and to support high-capacity service of high quality for user demands as well as voice services is recognized. The LTE system provides the improvements of low transmission delay, a high transmission rate, a system capacity, and coverage.
To this end, the LTE system supports a carrier aggregation (hereinafter referred to as a ‘CA’). The CA means the support of a plurality of carriers and is also called a spectrum aggregation or a bandwidth aggregation. That is, the CA supports multiple component carriers so that data can be transmitted and/or received in a broad band through a plurality of carriers. In this case, each of carriers bundled by a CA is called a component carrier (CC). Each component carrier is defined by a bandwidth and a center frequency.
In order to support the high transmission rate, that is, in order to increase a transmission capacity, to increase the bandwidth may be said to be essential, and to support a large bandwidth when a level of required service is low may cause great power consumption. Meanwhile, a base station may use information about the power of user equipment as a scheme for efficiently using the resources of the user equipment. Such a power control technology of the base station is an essential core technology for minimizing interference factors and reducing the battery consumption of user equipment in order to efficiently distribute resources in wireless communication. To this end, user equipment may determine uplink transmission power based on transmit power control assigned by a base station, a modulation and coding scheme (MCS), and scheduling information, such as a bandwidth.
Furthermore, control of the power of user equipment encounters a more complicated situation because pieces of uplink transmission power of respective component carriers need to be comprehensively taken into consideration due to the introduction of multiple component carriers. The complexity may cause problems in terms of maximum transmission power of user equipment. In general, user equipment needs to operate with power lower than maximum transmission power, that is, transmission power of a permissible range. If a base station performs scheduling that requires transmission power higher than the maximum transmission power, there may be a problem in that actual uplink transmission power exceeds maximum transmission power of user equipment. Accordingly, there is a need to clearly define uplink transmission power of user equipment in which multiple component carriers are taken into consideration.